When Should Teens Date?

I just found out from another parent that my 13 year old son has his first “girlfriend”. He has known the girl since kindergarten, she is very nice and they haven’t actually “gone” anywhere together, but 1) he didn’t tell me about it and 2) he seems a bit young for this already. Has anyone else had this experience? How did you handle it?

Image of Teens
By SCA Svenska Cellulosa Aktiebolaget via Wikimedia Commons